1. Field of the Invention
The present invention relates to the field of local area networks (LANs) using the Ethernet communication protocol (e.g., the IEEE 802.3 Standard). Specifically, the present invention relates to a switchable component within a network repeater hub.
2. Description of Related Art
Communication networks for computer systems are an extremely popular form of providing network computing today. FIG. 1 illustrates a high level block diagram of the communication levels within a typical communication network system 5. System 5 has a first communication level 12 including communication adapters (xe2x80x9ccardsxe2x80x9d) that are inserted into computer systems to provide them with networking capability. The computer systems interface with users 10. The second communication level 14 is the workgroup level and includes hubs (e.g., repeater hubs, switching hubs, etc.). The hubs provide communication pathways between computer systems of the same or multiple local area networks (LANs). Computer systems coupled to a common hub share the same collision domain. A collision domain is a group of computer systems logically connected to share the same physical bandwidth (e.g. 10 Megabits/sec or 100 Megabits/sec) of a communication pathway. In the field of twisted pair cable repeater hubs, a collision domain is managed by a Repeater Interface Controller (RIC). The third level 16 is often called the backbone or backplane level and can include segment switches. Among other functions, the components of level 16 provide communication pathways between hubs and between different collision domains.
Recently, 100 Megabit bandwidth networking (100 M or 100) has been introduced into the marketplace of computer network systems from an installed base of 10 Megabit bandwidth systems (10 M or 10). This has led to the development of dual rate adapter cards (e.g., of level 12) that can be configured to communicate at 100 M or 10 M; these dual rate adapters are referred to as 10/100 adapters. The IEEE 802.3 standard provides for an auto-negotiation session whereby the 10/100 adapter can determine which communication rate is supported by its coupled hub (e.g., of level 14). However, as described in more detail below, many of the workgroup hubs in level 14 do not support 100 M networking because of the additional cost required to upgrade the workgroup equipment to this rate.
For instance, refer to FIG. 2A which illustrates a prior art communication system 44 employing two repeater hubs 30 and 32. Repeater hubs are low cost because they do not require an expensive Media Access Controller (MAC) for each port nor do they require switches; only a physical device (e.g., 21a-21d or 23a-23d) is required at each port to provide repeating. Within system 44, all ports of a repeater hub (the hub having one repeater interface controller, RIC) are required to be of the same communication rate because: (1) messages from one port are repeated to all other ports by the hub""s RIC; and (2) because only one RIC is provided, only one collision domain is allowed. Therefore, 10/100 adapters 20a-20d are coupled to repeater hub 30 operating at 10 M while 10/100 adapters 22a-22d are coupled to repeater hub 32 operating at 100 M. The adapters 20a-20d and 22a-22d are coupled to their associated hubs through physical devices 21a-21d and 23a-23d, respectively. The repeater hubs 30 and 32 are coupled to backbone circuit 40 through pathways 34 and 36, respectively. Backbone circuit 40 may contain segment switches or routers. Due to the difference in operational speeds of hubs 30 and 32, the only means by which the two hubs can communicate is through backbone level 40, which has circuits that can adapt the data from each segment.
FIG. 2B illustrates a similar prior art communication system 78 using three exemplary stackable low cost repeater hubs 50a, 50b and 54 that each use a single RIC. Hubs 50a and 50b operate at 10 M while hub 54 operates at 100 M. Hubs 50a and 50b are coupled to switch module 62 via separate pathways 52a and 52b, respectively, while hub 54 is coupled to switch module 62 via separate pathway 56. The switch module 62 provides communication between the different collision domain segments. This can be accomplished either using a bus based CPU architecture or a cross bar switch architecture. A management module 64 is also included and interfaces with the switch module 62.
In systems like system 44 and system 78 (FIGS. 2A and 2B), the majority of installed repeater hubs support only 10 M communication (e.g., 10 Base T). If one port of a 10 M repeater hub (e.g., hub 30 or a hub of hubs 50a and 50b) needs to be upgraded to 100 M, all ports within the 10 M repeater hub need to be upgraded because the hub only supports collision domain. This causes a problem because the cost of performing such an upgrade for all ports in a 10 M repeater hub is very expensive and can be impractical if only one port needs the 100 M communication rate. The prior art solution for providing 100 M communication has been to add repeaters, e.g., repeater hub 54, that handle only 100 M communication. However, this solution has drawbacks when a computer system moves from one port to another. For instance, if system 44 includes ten 10 M hubs like hub 30 and only one 100 M hub like hub 32 and then adapter 22a is moved from one building to another, adapter 22a may no longer be physically accessible to hub 32. The same is true for system 78. It would be advantageous to provide a low cost repeater hub design that offers the flexibility of readily upgrading one or more ports of the hub to 100 M while allowing the remainder ports to operate at 10 M without requiring expensive switching circuitry. The present invention provides such a repeater hub.
FIG. 3 illustrates a high cost communication network 96 based on a switching hub 90 that provides mixed 10 M and 100 M ports. Adapters 80a-80h of the 10/100 type are coupled via respective physical devices 81a-81h to switching hub 90. Switching hub 90 contains complex circuitry 92 to provide multiple independent communication channels between respective pairs of adapters 80a-80h. Switching hub 90 allows for mixed 10 M and 100 M ports because independent communication channels can be formed between adapter pairs. However, system 96 is a very expensive network solution due to the required switching logic. For instance, the cost per port of the switching hub 90 is well over an order of magnitude greater than the cost per port of repeater system 44 (FIG. 2A) or repeater system 78 (FIG. 2B). For many network applications, the use of switching hub 90 is not a practical solution for providing mixed 10 M and 100 M ports within a workgroup hub because of its high cost per port. It would be advantageous to provide a workgroup hub that offers the flexibility of mixed 10 M and 100 M ports while avoiding the high cost per port associated with switching hubs. The present invention provides such a repeater hub.
Lastly, some repeater hubs incorporate more than one RIC circuit allowing a mixture of both 10 M and 100 M ports within a single 10/100 repeater hub. However, these 10/100 repeater hubs, as well as the repeater hubs of system 44 and system 78, use prior art physical devices to recover information at the port connection. As shown in FIG. 4, the physical device circuits 100 of the prior art, while supporting either 10 Base T 106 or 100 Base T 108 communication, nevertheless offer only one media independent interface (MII) 104. Therefore, each port within the prior art 10/100 repeater hub (using physical device 100) is hardwired to communicate within one, and only one, collision domain 102 (e.g., 100 M domain or 10 M domain). While allowing mixed 10/100 port assignments, this prior art 10/100 repeater hub is not flexible with respect to changes in the computer system coupled to a particular port. For instance, if a particular port is operating at 100 M and the user for that port is replaced with another user that does not need 100 M, a significant amount of reconfiguration is required (e.g., by a system administrator or communication technician) to rewire the particular port into another collision domain or wire another user into the particular port. Alternatively, if the particular port is not rewired, then resource bandwidth becomes wasted as 100 M is being reserved for a possible 10 M use. It would be advantageous to provide a low cost 10/100 repeater hub that provides port-by-port flexible reconfiguration between multiple collision domains without requiring expensive switching circuitry. The present invention provides such a repeater hub.
In other implementations of the circuit of FIG. 4, separate circuitry is applied external to the physical device 100 and this external circuitry acts as a switch circuit between multiple segments. The switch circuitry is typically coupled to a serial management port and an external controller. However, such design also typically requires processor intervention for providing switching activity; again leading to a complex and expensive solution. It would be advantageous to provide a low cost 10/100 repeater hub that provides port-by-port flexible reconfiguration between multiple collision domains without requiring expensive switching circuitry external to the physical device for each port of the hub.
Accordingly, the present invention provides a low cost repeater hub that offers the flexibility of readily upgrading one or more ports of the hub to 100 M while allowing the remainder ports to operate at 10 M. The present invention provides workgroup repeater hub that offers the flexibility of mixed 10 M and 100 M ports while avoiding the high cost per port associated with switching hubs. The present invention provides a low cost 10/100 repeater hub with port-by-port flexible reconfiguration between multiple collision domains without external switching circuitry applied to the physical device. The present invention provides such a repeater hub with a novel switching physical device. These and other advantages of the present invention not specifically mentioned above will become clear within discussions of the present invention presented herein.
A multi-communication rate switching physical device is described herein for a port of a mixed communication rate Ethernet repeater network. When integrated within a 10/100 repeater hub of the present invention, the present invention provides a low cost solution allowing an installed based of 10/100 adapters to advantageously communicate at 100 M.
The present invention includes a physical device for recovering bits from a wire connection (e.g., fiber, twisted pair, etc.) that is coupled to an adapter of a computer system. The physical device can be implemented on a single chip integrated within an Ethernet repeater hub within each hub port. The physical device chip of the invention includes a front end multiplexer coupled to channel information between a 10 Base T physical device circuit and a 100 Base T physical device circuit, depending on the result of an auto-negotiation circuit also on the physical device chip. The physical device chip also advantageously employs a second, back end multiplexer, that is coupled to channel data between (1) either the 10 Base T physical device circuit or the 100 Base T physical device circuit and (2) one of a multiple of media independent interfaces (MIIs). The back end multiplexer is controlled by a combination of signals including the result of the auto-negotiation circuit and a system management interface override signal.
By providing multiple MII (or giga MII) interface connections, the invention provides a low cost solution allowing the associated port to be automatically associated with one of a number of different collision domains within the Ethernet network. Therefore, separate ports within a same repeater hub (or configuration of stackable repeater hubs) can be assigned to different collision domains without requiring expensive switching equipment. In one particular embodiment, the present invention provides an Ethernet 10/100 repeater hub allowing ports of one group of the 10/100 repeater hub to be assigned to a 100 Base T domain and ports of another group of the 10/100 repeater hub to be assigned to a 10 Base T domain. Port assignment to one domain or another is flexible and can be based on: (1) the result of an auto-negotiation session; (2) a manual override; or (3) detected errors in the fastest attempted rate. By allowing ports of a 10/100 repeater hub to be readily upgraded to 100 M communication, the present invention is a low cost solution allowing the installed based of 10/100 adapters to advantageously communicate at 100 M.
Specifically, embodiments of the present invention include a switchable physical device circuit integrated on a semiconductor substrate for interfacing with an adapter of a computer system, the switchable physical device circuit comprising: a first physical device circuit (e.g., Ethernet 10 Base T) operable at a first communication rate; a second physical device circuit (e.g., Ethernet 100 Base T) operable at a second communication rate; an auto-negotiation circuit for determining if the adapter is able to communicate at the second communication rate and generating a result signal indicative thereof; a front end multiplexer controlled by the result signal and for multiplexing information between the adapter and one of the first and the second physical device circuits; a first media independent interface circuit for communicating with a first collision domain; a second media independent interface circuit for communicating with a second collision domain; and a back end multiplexer controlled by the result signal and for multiplexing information between one of the first and the second physical device circuits and one of the first and the second media independent interface circuits. Embodiments of the present invention also include a repeater hub implemented with switchable physical devices as described above.